U.S. patent number 7,905,799 [Application Number 12/273,752] was granted by the patent office on 2011-03-15 for golf club head.
This patent grant is currently assigned to SRI Sports Limited. Invention is credited to Masaru Kouno, Tomio Kumamoto.
United States Patent |
7,905,799 |
Kouno , et al. |
March 15, 2011 |
Golf club head
Abstract
The invention prevents a resin member from being broken so as to
improve durability. The invention provides a golf club head (1) in
which at least a part of a crown portion (4) forming an upper
surface of the head is formed by a resin member (FR) made of a
fiber reinforced resin in which a fiber is oriented in a matrix
resin. The resin member (FR) includes a one-way fiber reinforced
resin layer in which the fiber is oriented in one direction, and a
fiber intersection lamination portion which is laminated so as to
differentiate a direction of the fiber. At least two one-way fiber
reinforced resin layers which are adjacent in a thickness direction
are intersected at an angle of 30 to 130 degrees of the fiber.
Further, a compressive strength of the fiber of the one-way fiber
reinforced resin layer which is arranged in an innermost side in
the fiber intersection lamination portion is set to be equal to or
more than 1.3 GPa.
Inventors: |
Kouno; Masaru (Kobe,
JP), Kumamoto; Tomio (Kobe, JP) |
Assignee: |
SRI Sports Limited (Kobe,
JP)
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Family
ID: |
35187812 |
Appl.
No.: |
12/273,752 |
Filed: |
November 19, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090176600 A1 |
Jul 9, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11103555 |
Apr 12, 2005 |
7468005 |
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Foreign Application Priority Data
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Apr 28, 2004 [JP] |
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2004-133936 |
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Current U.S.
Class: |
473/345;
473/347 |
Current CPC
Class: |
A63B
53/0466 (20130101); A63B 60/00 (20151001); A63B
53/0408 (20200801); A63B 2209/00 (20130101); A63B
53/0458 (20200801); A63B 2209/023 (20130101); A63B
53/0475 (20130101); A63B 53/0437 (20200801); A63B
53/0487 (20130101); A63B 53/047 (20130101) |
Current International
Class: |
A63B
53/04 (20060101) |
Field of
Search: |
;473/324-350 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2003-111874 |
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Apr 2003 |
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JP |
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2005-058634 |
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Mar 2005 |
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JP |
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Primary Examiner: Hunter; Alvin A
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a 37 C.F.R. .sctn.1.53(b) Continuation
application of U.S. application Ser. No. 11/103,555 filed Apr. 12,
2005 (now U.S. Pat. No. 7,468,005), which in turn claims priority
on Japanese Application No. 2004-133936 filed Apr. 28, 2004. The
entire contents of each of these applications are hereby
incorporated by reference.
Claims
What is claimed is:
1. A golf club head comprising a face portion, a crown portion, a
sole portion, a side portion and a neck portion, in which said club
head is formed from a head main body having an opening portion, and
a resin member which constitutes at least a part of the crown
portion forming the upper surface of the head and which is made of
a fiber reinforced resin containing a fiber oriented in a matrix
resin, said head main body has a crown receiving portion around the
opening portion, said resin member has a fork portion comprising an
outer piece and an inner piece portion, and said fork portion
pinches said crown receiving portion so as to cover said opening
portion with said resin member, wherein said resin member includes
a fiber intersection lamination portion where one-way fiber
reinforced resin layers are laminated, in which the fiber in each
of said one-way fiber reinforced resin layers is oriented in one
direction, and the fibers of adjacent two one-way fiber reinforced
resin layers are oriented in a different direction from each other,
said resin member comprises a base portion which forms a part of
the crown portion, and a trailing portion which is bend downward
from the base portion and forms a part of the side portion, and
said resin member is arranged in a head main body M made of a metal
material having an opening portion at least in the crown portion to
cover the opening portion, each of said one-way fiber reinforced
resin layers is formed of a sheet-like one-way prepreg in which the
fiber is oriented in one direction in an uncured matrix resin and
which is provided with a plurality of slits in a peripheral edge on
the side portion side of the prepreg in order to easily form said
trailing portion by bending the peripheral edge, and said resin
member is composed of said fiber intersection lamination portion
and an outer surface layer of a single intersecting
fiber-reinforced resin layer in which fibers extend in at least two
directions.
2. The golf club head of claim 1, wherein said fibers in said
single intersecting fiber-reinforced resin layer is composed of a
fiber extending at an angle of substantially 0.degree. and a fiber
extending at an angle of substantially 90.degree., respectively,
with respect to a base line BL extending in the head longitudinal
direction.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a golf club head in which a resin
member made of a fiber reinforced resin is employed at least in a
part of a crown portion.
In recent years, for example, as described in Japanese Published
patent application 2003-111874, there has been proposed a so-called
compound type golf club head formed by firmly fixing a resin member
structuring a part of a crown portion and made of a fiber
reinforced resin, and a head main body made of a metal
material.
The composite type golf club head as mentioned above can reduce its
weight by using a fiber reinforced resin having a small specific
gravity. Accordingly, for example, it is possible to enlarge a head
volume. Further, the reduced weight can be more distributed in a
side portion of a head, for example, a toe or a heel, a back face
and the like. These can increase a moment of inertia around a
gravity point of the head and increase a depth of center of gravity
point. Further, if the fiber reinforce resin is used in the crown
portion, it is possible to reduce a weight of an upper portion side
of the head, so that it serves for achieving a low gravity point.
As mentioned above, in the composite head, it is possible to
increase a freedom of designing the weight distribution.
However, in the composite type golf club mentioned above, breakage
of the resin member tends to be generated due to an impact at the
time of hitting a ball. In order to prevent the resin member from
being broken, there can be considered to make a thickness of the
resin member large, however, in accordance with this method, it is
impossible to obtain a substantial weight reducing effect by the
resin member. As mentioned above, in the composite type head, there
is a room for further improving durability. Accordingly, in the
composite type head, it can be said that an improvement is
necessary while paying attention to an angle of orientation of the
fiber in the resin member and a strength or an elastic modulus
included in a matrix resin.
BRIEF SUMMARY OF THE INVENTION
The present invention is made by taking the actual condition
mentioned above into consideration, and an object of the present
invention is to provide a golf club head which can inhibit a resin
member from being broken in accordance with an impact at the time
of hitting a ball for a long time so as to improve durability. The
golf club head of the present invention is based on a structure of
a resin member so as to include a fiber intersection lamination
portion in which one-way fiber reinforced resin layers having the
fibers distributed in one direction are laminated in a state of
differentiating directions of the fibers, limiting an angle of
intersection of the fiber in at least two one-way fiber reinforced
resin layers which are adjacent in a thickness direction, and
limiting a compressive strength of the fiber of the one-way fiber
reinforced resin layer which is arranged in an innermost side in
the fiber intersection lamination portion to a fixed value or
more.
In this case, the compressive strength of the fiber is determined
on the basis of the following procedure. First, there is prepared a
test piece made of a fiber reinforced resin obtained by binding a
fiber serving as a subject to be measured by a specific resin
composition material described in detail below. Further, a
compressive strength of the test piece is measured by using a
compressing jig shown by ASTMD695 and under a condition of a strain
rate 1.27 mm/min. The compressive strength of the fiber is
calculated by setting a fiber volume fraction to 60% on the basis
of the compressive strength of the test piece.
Further, the specific resin composition material is obtained by
mixing the following raw material resin and agitating them for
thirty minutes.
Bisphenol A Diglycidyl Ether Resin: 27 weight %
"Trade name: Epicoat 1001 (manufactured by YUKA SHELL EPOXY CO.,
LTD., Registered Trade Mark)"
Bisphenol A Diglycidyl Ether Resin: 31 weight %
"Trade name: Epicoat 828 (manufactured by YUKA SHELL EPOXY CO.,
LTD., Registered Trade Mark)"
Phenolic Novolac Polyglycidyl Ether Resin: 31 weight %
"Trade name: Epiclon-N740 (manufactured by Dainippon Ink &
Chemicals, Inc., Registered Trade Mark)"
Polyvinyl Formal Resin: 3 weight %
"Trade name: Vinylex K (manufactured by Chisso CO., LTD., Trade
Mark)"
Dicyandiamide: 41 weight %
"Trade name: DICY 7 (manufactured by Dainippon Ink & Chemicals,
Inc., Registered Trade Mark)"
3,4-dichlorophenyl-1,1-dimethyl urea: 4 weight %
"Trade name: DCMU99 (manufactured by Hodogaya Chemical Co., Ltd,
curing agent)"
Next, a resin film obtained by coating the resin composition
material on a silicone coating paper is wound around a steel drum
which is controlled so as to have a circumference of about 2.7 m
and a temperature of 60 to 70.degree. C. The fiber serving as the
subject to be measured wound off from a creel is arranged thereon
along a circumferential direction via a traverse. Further, the
resin film is rearranged thereon and the resin is impregnated in
the fiber by pressurizing the resin film while rotating by a roll.
Accordingly, it is possible to manufacture a one-way prepreg having
a width of 300 mm and a length of 2.7 m. In this case, a fiber
weight amount of the prepreg is regulated to 190 g/m.sup.2, and a
resin percentage content is regulated to 35 weight %.
Further, the one-way prepreg is laminated while aligning in a fiber
direction, and is cured for two hours at a temperature of
130.degree. C. and a pressure of 0.3 MPa, whereby a laminated plate
having a thickness of 1 mm is formed. A plate for reinforcing the
other portions than a broken portion of the test piece is firmly
fixed to the laminated plate by an adhesive agent. A thickness of
the adhesive layer is set uniform. The test piece is prepared from
this laminated plate by being cut out at a thickness of about
1.+-.0.1 mm, a width of 12.7.+-.0.13 mm, a length of 80.+-.0.013
mm, and a length of a gauge portion of 5.+-.0.13 mm, such that the
broken portion forms a center.
In the invention, a tensile strength of the fiber in the one-way
fiber reinforced resin layer which is arranged in an outermost side
May be equal to or more than 3.5 GPa, in said fiber intersection
lamination portion.
In this case, with respect to a tensile strength of the fiber, a
resin impregnated strand is formed by impregnating an epoxy resin
composition material in the fiber corresponding to the subject to
be measured, and heating it for thirty minute at 130.degree. C. so
as to cure. Further, the tensile strength is determined in
accordance with a resin impregnated strand testing method shown in
JIS R7601. The epoxy resin composition material is prepared by
using the following raw material resin.
Bakelite (Registered Trade Mark): 1000 g (930 weight %)
"Trade name: ERL-4221, manufactured by Union Carbide Co., Ltd."
Boron trifluoride mono-ethylamine (BF3.cndot.MEA): 30 g (3 weight
%)
Acetone: 40 g (4 weight %)
Also, a golf club head in the invention, the fiber intersection
lamination portion May be constituted by at least three one-way
fiber reinforced resin layers, and compressive strength of the
fiber .sigma.c1, .sigma.c2, .sigma.cn (n is an integer equal to or
more than 3) of the one-way fiber reinforced resin layers
sequentially from that arranged in the inner side, can satisfy the
following expressions (1) and (2). .sigma.
c1>.sigma.c2>>.sigma.cn (1) .sigma.c1>.sigma.cn (2)
And besides, the fiber intersection lamination portion May be
constituted by at least three one-way fiber reinforced resin
layers, and tensile strength of the fiber .sigma.t1, .sigma.t2,
.sigma.tn (n is an integer equal to or more than 3) of the one-way
fiber reinforced resin layers sequentially from that arranged in
the inner side, may satisfy the following expressions (3) and (4).
.sigma.t1<.sigma.t2<<.sigma.tn (3) .sigma.t1<.sigma.tn
(4)
Additionally, the resin member May include a fiber woven portion in
which the fibers extending at least in two directions, at an outer
side of said fiber intersection lamination portion.
Since the golf club head in accordance with the present invention
has the structure mentioned above, at least a part of a crown
portion forming an upper surface of the head is formed by the resin
member made of the fiber reinforced resin in which the fiber is
oriented in the matrix resin. Accordingly, it is possible to reduce
the weight of the upper portion side of the head so as to serve for
achieving a low gravity point. Further, the resin member includes
the fiber intersection lamination portion, in which the direction
of the fiber of the one-way fiber reinforced resin layers is
oriented in different direction. Further, at least two one-way
fiber reinforced resin layers which are adjacent in the thickness
direction are intersected at an angle of 30 to 90 degrees of the
fiber. Accordingly, it is possible to increase a strength against a
stress in multi directions generated in the resin member at the
time of hitting the ball, and it is possible to improve durability
by extension.
Further, a large compression stress is applied to an inner side of
the resin member provided in the crown portion of the head at the
time of hitting the ball. The compressive strength of the fiber of
an innermost one-way fiber reinforce resin layer which is arranged
in an innermost side in the fiber intersection lamination portion
is set to be equal to or more than 1.3 GPa which is larger than the
conventional one. Accordingly, it is possible to increase a
strength of an inner side of the resin member, and it is possible
to effectively prevent the breakage. In this case, since the
tensile strength is generated in an outer side of the resin member
inversely to the inner side, it is possible to further improve the
durability of the resin member by setting the tensile strength of
the fiber in the one-way fiber reinforced resin layer which is
arranged in the outermost side to be equal to or more than 3.5
Gpa.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a perspective view of a standard condition of a head
showing an embodiment in accordance with the present invention;
FIG. 2 is a plan view of the same;
FIG. 3 is an enlarged cross sectional view along a line A-A in FIG.
2;
FIG. 4 is an enlarged cross sectional view along a line B-B in FIG.
2;
FIG. 5 is an exploded perspective view of the head;
FIG. 6 is an enlarged view of a portion X in FIG. 3;
FIG. 7 is a partial exploded plan view of FIG. 6;
FIG. 8 is a partial exploded plan view of FIG. 6 showing another
embodiment;
FIGS. 9(A) and 9(B) are plan skeleton views showing a direction of
a main stress applied to a crown portion at the time of hitting a
ball;
FIG. 10(A) is a cross sectional view rhetorically showing a
deformed state of the head at the time of hitting the ball;
FIG. 10(B) is a partial enlarged view of a resin member in a crown
side thereof;
FIG. 11 is a graph showing a relation between a tensile strength
and an elastic modulus in tension of a carbon fiber;
FIGS. 12(A) to 12(E) are plan views of a prepreg;
FIGS. 13(A) to 13(E) are plan views of a prepreg showing another
embodiment;
FIGS. 14(A) and 14(B) are cross sectional views describing an
internal pressure molding method; and
FIG. 15 is a partial cross sectional view showing another
embodiment of the internal pressure molding method.
DETAILED DESCRIPTION OF THE INVENTION
A description will be given below of an embodiment in accordance
with the present invention on the basis of the accompanying
drawings.
FIG. 1 shows a perspective view of a standard condition in which a
golf club head (hereinafter, sometimes refer simply to as a "head")
1 in accordance with the present embodiment is grounded on a
horizontal surface while holding the head 1 at prescribed lie angle
and loft angle (real loft angle), FIG. 2 shows a plan view of the
same, FIG. 3 shows an enlarged cross sectional view along a line
A-A in FIG. 2, FIG. 4 shows an enlarged cross sectional view along
a line B-B in FIG. 2, and FIG. 5 shows an exploded perspective view
of FIG. 1, respectively.
The head 1 in accordance with the present embodiment is provided
with a face portion 3 having a face surface 2 corresponding to a
surface for hitting a ball, a crown portion 4 connected to the face
portion 3 and forming an upper surface of the head, a sole portion
5 connected to the face portion 3 and forming a bottom surface of
the head, a side portion 6 joining between the crown portion 4 and
the sole portion 5 and extending from a toe 3a of the face portion
3 to a heel 3b through a back face, and a neck portion 7 provided
in a heel side of the crown portion 4 and attached to one end of a
shaft (not shown). Further, the head can be structured as a wood
type head such as a driver (#1) or a fairway wood having a hollow
structure provided with a hollow portion i in an inner portion, and
is exemplified as the driver (#1) in the present embodiment.
Further, in the head 1, at least a part of the crown portion 4 is
formed by a resin member FR made of a fiber reinforced resin. The
head 1 in accordance with the present embodiment is exemplified by
a structure which is formed by using a head main body M which is
provided with an opening portion O and is made of a metal material,
and the resin member PR which is arranged so as to cover the
opening portion O and is made of the fiber reinforced resin. The
opening portion O is provided in the crown portion 4 in this
embodiment by only one, and the resin member FR is constituted by a
crown side resin member FR1 covering the opening portion O.
The head main body M is formed, as shown in FIG. 5, so as to
include the face portion 3, the sole portion 5, the neck portion 7,
a crown edge portion 10 formed around the opening portion O and a
side wall portion 11. The head main body M may be manufactured, for
example, by previously forming each of portions integrally in
accordance with casting or the like. Further, the head main portion
M may be manufactured by forming two or more parts in accordance
with forging, casting, pressing, rolling or the like and thereafter
integrally bonding them in accordance with a welding or the
like.
A metal material of the head main body M is not particularly
limited, however, can employ, for example, a stainless steel, a
maraging steel, a titanium, a titanium alloy, an aluminum alloy, a
magnesium alloy, an amorphous alloy or the like, and can especially
employ one or two or more of the titanium alloy, the aluminum alloy
and the magnesium alloy which have a large specific strength, and
particularly preferably employs the titanium alloy.
As shown in FIGS. 4 and 5, the crown edge portion 10 in accordance
with the present embodiment includes a crown surface portion 10a
forming a substantial outer surface portion of the crown portion 4,
and a crown receiving portion 10b in which a surface is depressed
from the crown surface portion 10a to the hollow portion i side
while having a step. Further, the side wall portion 11 in
accordance with the present embodiment includes a side surface
portion 11a forming a substantial outer surface portion of the side
portion 6, and a side receiving portion 11b in which a surface is
depressed from the side surface portion 11a to the hollow portion i
side while having a step.
Each of the receiving portions 10b and 11b is bonded to an inner
surface of the resin member FR1 in the crown side and a peripheral
edge portion thereof, whereby the crown side resin member FR1 and
the head main body M are integrally formed. Further, each of the
receiving portions 10b and 11b absorbs a thickness of the crown
side resin member FR1 on the basis of the step mentioned above, and
serves for finishing each of the outer surfaces of the resin member
FR1 and the head main body M (the crown surface portion 10a and the
side surface portion 10 b) in a flush manner.
In this embodiment, the crown receiving portion 10b and the side
receiving portion 11b are connected around the opening portion O.
Accordingly, the annularly continuous receiving portion is formed.
A width (a length measured along the surface of the receiving
portion) Wa of the receiving portions 10b and 11b measured in a
perpendicular direction from an edge of the opening portion O is
not particularly limited. However, if the width is too short, a
joint area between the head main body M and the crown side resin
member FR1 becomes small, so that a bonding strength tends to be
lowered. On the contrary, if it is too long, an area of the opening
portion O becomes small, so that there is a tendency that a weight
saving effect can not be sufficiently obtained. From this point of
view, for example, it is desirable that the width Wa is equal to or
more than 5.0 mm, and preferably equal to or more than 10.0 mm, and
it is desirable that an upper limit is equal to or less than 30.0
mm, more preferably equal to or less than 20.0 mm, and particularly
preferably equal to or less than 15.0 mm. In this case, in the
present embodiment, the width Wa is exemplified as being changed in
each of the portions.
The crown side resin member FR1 is structured by a fiber reinforced
resin corresponding to a compound material of a matrix resin and a
fiber f.
As the matrix resin R, for example, it is possible to employ a
thermosetting resin such as an epoxy resin, a phenol resin, a
polyester resin or an unsaturated polyester resin, as well as a
thermoplastic resin such as a polycarbonate resin or a nylon resin.
In the present embodiment, the epoxy resin is used in view of a
cost and a general-purpose property.
As the fiber f mentioned above, for example, it is desirable to
employ one or more of a carbon fiber, a graphite fiber, a glass
fiber, an alumina fiber, a boron fiber, an aromatic polyester resin
fiber, an aramid resin fiber or a PBO resin fiber, or an amorphous
fiber or a titanium fiber, and the like, and particularly, the
carbon fiber in which a specific gravity is small and a tensile
strength is large is preferably employed. The fibers f are
structured as a short fiber, a long fiber or both. The long fiber
is used in the present embodiment.
An elastic modulus of the fiber f is not particularly limited,
however, if it is too small, it is impossible to secure a rigidity
of the resin member FR and there is a tendency that the durability
is lowered. On the other hand, if it is too large, there is a
tendency that the tensile strength is lowered as well as a cost is
increased. From this point of view, it is desirable that the
elastic modulus of the fiber is equal to or more than 50 GPa, more
preferably equal to or more than 100 GPa, further preferably equal
to or more than 150 GPa, and particularly preferably equal to or
more than 200 GPa. Further, an upper limit thereof is preferably
set to be equal to or less than 500 GPa, more preferably equal to
or less than 450 GPa, and further preferably equal to or less than
400 GPa. The elastic modulus mentioned above corresponds to an
elastic modulus in tension and is a value measured in accordance
with a "carbon fiber test method" in JIS R7601.
Further, the crown side resin member FR1 is arranged in a head main
body M so as to cover the opening portion O, as shown in FIGS. 1 to
5. Further, in the present embodiment, the resin member FR1 is
exemplified as a structure which includes a base portion 12 forming
a part of the crown portion 4, and a trailing portion 13 bent from
the base portion 12 and forming a part of the side portion 6. Since
the crown side resin member FR1 having the shape mentioned above is
bonded to each of the crown receiving portion 10b and the side
receiving portion 11b in the peripheral edge of the base portion
12, an adhesive interface is provided in the crown portion 4 and
the side portion 6 so as to be diversified, and it is possible to
achieve a high adhesive strength against an external force applied
from various directions. Since the trailing portion 13 forms a
surface which is bent at an angle close to an approximately right
angle from the crown receiving portion 10b, it is possible to
improve the strength.
FIG. 6 shows an enlarged cross sectional view of the crown side
resin member FR1 corresponding to an enlarged view of a portion X
in FIG. 3. In this drawing, only a matrix resin R is drawn and a
reinforcing fiber is omitted. Further, FIG. 7 shows a plan view in
which a part of FIG. 6 is broken, for the purpose of easily
understanding a laminated state of the layers.
The resin member FR1 in the crown side is exemplified by a
structure constituted by five fiber reinforced resin layers having
different fiber orientation directions in accordance with the
present embodiment. Specifically speaking, the resin member FR1 in
the crown side in accordance with this embodiment is structured
such as to include a fiber intersection lamination portion 8 in
which four one-way fiber reinforced resin layers L1 to L4 are
laminated, and a fiber woven portion 9 constituted by one
intersection fiber reinforced resin layer L5 arranged in an outer
side thereof. The outer side fiber woven portion 9 forms an outer
surface A of the resin member FR1. Including a plurality of fiber
reinforced resin layers having the different fiber orientation
directions as mentioned above serves for uniformly dispersing the
stress with respect to a thickness direction of the resin member
FR1. Accordingly, it is desirable that the fiber intersection
lamination portion 8 is preferably constituted by at least three or
more one-way fiber reinforced resin layers.
Each of the one-way fiber reinforced resin layers L1 to L4
mentioned above is structured such that the fiber f is oriented in
the matrix resin R in one direction. Accordingly, for example, a
reinforced resin layer having a woven fabric fiber obtained by
alternately weaving warp or warps and weft or wefts is not included
in the one-way fiber reinforced resin layer. Further, as shown in
FIG. 7, at least two one-way fiber reinforced resin layers which
are adjacent in the thickness direction are structured such that
the respective fibers f are intersected at an angle .alpha. of 30
degrees to 90 degrees in the fiber intersection lamination portion
8. The angle .alpha. is a relative angle between the intersecting
fibers, and means an acute angle (except 90 degrees).
In the present embodiment, the one-way fiber reinforced resin L1
arranged in the innermost side has a fiber f which is oriented in
one direction substantially having an angle of -45 degrees (the
angle is set to be positive in a counterclockwise direction) with
respect to a base line BL in a head longitudinal direction. In the
same manner, the one-way fiber reinforced resin layer L2 overlapped
in an outer side thereof has a fiber f which is oriented in a
direction in which the angle .theta. is 45 degrees, the one-way
fiber reinforced resin layer L3 overlapped in further an outer side
thereof has a fiber f which is oriented in a direction in which the
angle .theta. is -45 degrees, and the one-way fiber reinforced
resin layer L4 overlapped in further an outer side thereof has a
fiber f which is oriented in a direction in which the angle .theta.
is 45 degrees. Three interlayer boundary surfaces are formed by
overlapping four one-way fiber reinforced resin layers L1 to L4. In
this case, the base line BL in the head longitudinal direction
corresponds to a line segment in which a vertical surface including
a vertical line N drawn from a head gravity point G to the face
surface 2 intersects the resin member FR1 in a plan view (FIG. 2)
in the standard condition.
If the angle .alpha. at which the fiber f intersects is less than
30 degrees in the boundary surface of each of the layers, a large
strength anisotropy tends to be generated by these two one-way
fiber reinforced resin layers. As a result, in the case that the
stress is applied in the direction having a low strength, there is
a risk that the resin member FR1 is broken. Particularly
preferably, it is desirable that the angle .alpha. is set from 60
to 90 degrees, further preferably from 80 to 90 degrees, most
preferably from 85 to 90 degrees. In the present embodiment, there
is shown a particularly preferable aspect that the angles .alpha.
in all the boundary surfaces are substantially 90 degrees.
Further, in the fiber intersection lamination portion 8, it is
sufficient that the fibers of at least two one-way fiber reinforced
resin layers intersect at the angle .alpha. mentioned above. As in
the present embodiment, the angle .alpha. mentioned above is
preferably satisfied in all the one-way fiber reinforced resin
layers which are adjacent in the thickness direction.
Further, the angle .theta. formed between each of the fibers f in
the one-way fiber reinforced resin layers L1 to L4 and the base
line BL in the head longitudinal direction is not particularly
limited. For example, in the case of a general amateur golfer, it
is hard to correctly hit a golf ball at a sweet spot SS of the face
surface 2 (a point at which the vertical line N intersects the face
surface 2 as shown in FIG. 2), and the amateur golfer generally hit
the ball at a position which is deflected from the sweet spot SS to
a toe or heel (not shown) side as shown in FIG. 9(A).
At this time, a torsional deformation is generated crown portion 4
of the head 1. The deformation mentioned above mainly applies
inclined stresses a and b as shown in FIG. 9(A) with respect to the
base line BL in the head longitudinal direction to the resin member
FR1. Accordingly, in the case of aiming at the amateur golfer, it
is preferable to alternately arrange the angle .theta. of the
one-way fiber reinforced resin layer to 45 degrees and -45 degrees
as in the present embodiment so as to improve the strength against
the main stress direction. Further, the head 1 mentioned above
serves for inhibiting the torsional deformation mentioned above,
restricting the direction change of the face surface 2 to the
minimum, and stabilizing the directionality of the hit ball.
On the other hand, as for professional and senior golfers, as shown
in FIG. 9(B), in most cases, the ball is accurately hit at the
sweet spot SS, or the position near the sweet spot SS. At this
time, in the crown portion 4 of the head 1, in a direction of a
plain surface, there is mainly generated a stress c in a direction
in parallel to the base line BL of the head longitudinal direction,
and a stress d in a perpendicular direction thereto. Accordingly,
in the case of the head aiming at the senior golfer, as shown in
FIG. 8, it is effective to mainly improve the strength against the
stress direction by alternately arranging the angle .theta. of the
one-way fiber reinforced resin layer at 0 degrees and 90 degrees.
Further, in the head 1 as mentioned above, a restoring force is
larger after the resin member FR1 arranged in the crown portion 4
is deflected. This serves for increasing a repulsion property of
the face portion and hitting a ball longer away. In view of
increasing the repulsion property, it is preferable to arrange one
or more one-way fiber reinforced resin layer having the angle
.theta. of -10 to 10 degrees, more preferable to arrange two or
more layers. In this case, if the number of the one-way fiber
reinforced resin layer having the angle .theta. of -10 to 10
degrees is too large, the head becomes too heavy and a cost
increase tends to be caused. Accordingly, an upper limit of the
number of the one-way fiber reinforced resin layer having the angle
.theta. of -10 to 10 degrees is set to be equal to or less than
five, more preferably equal to or less than four, and particularly
preferably equal to or less than three.
Further, the angles .theta. and .alpha. mentioned above may employ
any values as far as the angles are satisfied at an optional
position on the base line BL in the head longitudinal direction of
the resin member FR1. Because a greatest stress tends to be
generated in this portion. It is not necessary that the angle 9 of
the fiber f is exactly an angle just corresponding to the numeric
value, and it is sufficient that the angle is a substantial value
obtained by taking a manufacturing error and a dispersion of the
material into consideration. For example, the angle .theta. of the
fiber f can allow at least a dispersion of -10 to +10 degrees (that
is, .+-.10 degrees), more preferably a dispersion of -5 to +5
degrees (that is, .+-.5 degrees).
Further, the fiber woven portion 9 arranged in an outer side of the
fiber intersection lamination portion 8 is structured, as shown in
FIG. 7, by one intersection fiber reinforced resin layer L5 having
at least fibers fa and fb extending in two directions. In an
example shown in FIG. 7, the fibers fa and fb are exemplified by
structures which have two directions substantially forming 0
degrees and 90 degrees with respect to the base line BL in the head
longitudinal direction, and are woven in a plain weave shape by
setting the fibers in the respective directions to the warp and
weft. A weaving method can employ various methods, for example, a
sateen weave, a twill weave and the like in addition to the plain
weave. Further, the fiber may be woven in a plain three-axis weave
or the like as far as two or more fibers in different directions
are provided. However, it is preferable to define the direction in
this case such that the angle of intersection of the fiber is
uniform. The intersection fiber reinforced resin layer L5 mentioned
above serves for uniformly dispersing the stress generated at the
time of hitting the ball. In particularly preferable, it is
desirable to differentiate the angle of orientation of the fibers
fa and fb from the angle of each of the fibers in the fiber
intersection lamination portion 8.
In this case, the base portion 12 of the resin member FR1 in the
crown side is smoothly curved so as to protrude to an upper side of
the head in the cross section in the base line BL in the head
longitudinal direction shown in FIG. 3, and in accordance with one
example, a radius of curvature rc of the outer surface A thereof is
set to about 55 to 130 mm. As shown in FIG. 10(A) and FIG. 10(B)
showing a part thereof by a rhetorically enlarging manner, in the
resin member FR1 in the crown side, a deflection (a bending
deformation) protruding toward the outer side of the head is
generated at the time of hitting the ball, on the basis of the
curved shape as mentioned above. The deformation mentioned above
applies a compression stress to an inner side of a neutral line Mc
of the bending of the resin member FR1 and applies a tensile stress
to an outer side thereof, respectively, and a magnitude of each of
them becomes maximum in each of the surfaces A and B.
On the other hand, in the fiber f of the fiber reinforced resin,
the compressive strength is smaller in comparison with the tensile
strength in the axial direction. Accordingly, it is possible to
estimate that any breakage is generated in most of the conventional
resin members due to the compression stress applied to the inner
side thereof. In the head 1 in accordance with the present
invention, the compressive strength of the one-way fiber reinforced
resin layer Li which is arranged in the innermost side in the fiber
intersection lamination portion 8 is set to be equal to or more
than 1.3 GPa which is larger than the conventional one.
Accordingly, it is possible to effectively prevent the resin member
FR1 in the crown side from being broken. Further, an elastic energy
stored in the resin member FR1 in the crown side deflected at the
time of hitting the ball generates a great kinetic energy pushing
back the face portion 3 at the time of restoring the deflection, by
increasing the compressive strength in the inner side of the resin
member FR1. This serves for improving a repulsing performance of
the head 1.
In the case that the compression strength of the resin member FR1
in the crown side is less than 1.3 GPa, it is impossible to
sufficiently intend to improve the strength. As a particularly
preferable aspect, it is desirable that the compressive strength is
equal to or more than 1.5 GPa, and more preferably equal to or more
than 1.6 GPa. In this case, since the larger compressive strength
is preferable, an upper limit thereof is not particularly limited,
however, can be practically set to about 1.8 GPa.
Further, in the fiber intersection lamination portion 8, an entire
thereof can be structured by the one-way fiber reinforced resin
layer having the same compressive strength, however, the
compression stress of the resin member FR1 in the crown side
generated at the time of hitting the ball is in proportion to a
distance from a bending neutral line Mc as shown in FIG. 10(B),
becomes maximum in an inner side surface B and becomes smaller
toward an outer side. Accordingly, it is desirable to make the
compressive strength of the fiber of each of the one-way fiber
reinforced resin layers in the fiber intersection lamination
portion 8 larger toward the inner side in correspondence to the
internal stress state of the resin member FR1 mentioned above.
Therefore, it is possible to use a low cost material in which the
compressive strength is relatively lowered, in the other one-way
fiber reinforced resin layer than the innermost side, and it is
possible to improve durability while maintaining a product
cost.
Specifically, on the assumption that the compressive strength of
the fiber of the one-way fiber reinforced resin layer in the fiber
intersection lamination portion 8 is sequentially set to .sigma.c1,
.sigma.c2, .sigma.cn (in this case, n is an integer equal to or
more than 3) from that arranged in the inner side, it is desirable
to satisfy the following expressions (1) and (2).
.sigma.c1>.sigma.c2>>.sigma.cn (1) .sigma.c1>.sigma.cn
(2)
Particularly, it is desirable that the expression (1) is the
following expression (1)', and the compressive strength is
differentiated in each of the layers.
.sigma.c1>.sigma.c2>>.sigma.cn (1)'
Further, in these cases, it is desirable that a difference
(.sigma.c1-.sigma.cn) between the compressive strength .sigma.c1 of
the fiber f in the innermost side one-way fiber reinforced resin
layer L1, and the smallest compressive strength .sigma.cn in the
other one-way fiber reinforced resin layer is preferably equal to
or more than 0.20 GPa, more preferably equal to or more than 0.25
GPa, and further preferably equal to or more than 0.30 GPa, and
upper limit thereof is preferably equal to or less than 0.60 GPa,
more preferably equal to or less than 0.55 GPa, and further
preferably equal to or less than 0.50 GPa. If the difference is
less than 0.20 GPa, it is impossible to apply a sufficient strength
difference, and it is hard to achieve the cost reduction. On the
contrary, if it is more than 0.60 GPa, the strength difference
becomes too large, and the breakage or the like tends to be
generated in the other one-way fiber reinforced resin layer.
Further, the tensile stress is generated in the outer side of the
resin member FR1 in the crown side at the time of hitting the ball,
as mentioned above. The tensile strength of the fiber f is larger
in comparison with the compressive strength, however, it is
possible to further increase the durability of the resin member FR1
in the crown side by inhibiting the value. Accordingly, it is
desirable that the tensile strength of the one-way fiber reinforced
resin layer L4 arranged in the outermost side is set to be equal to
or more than 3.5 GPa, more preferably equal to or more than 4.0
GPa, and further preferably equal to or more than 5.0 GPa,
preferably in the fiber intersection lamination portion 8 mentioned
above. In this case, since the larger tensile strength is
preferable, an upper limit thereof is not particularly limited,
however, can be set practically to about 6.0 GPa.
Further, in the fiber intersection laminated portion 8, an entire
thereof can be structured by the one-way fiber reinforced resin
layer having the same tensile strength. However, the tensile stress
of the resin member FR1 in the crown side generated at the time of
hitting the ball is in proportion to the distance from the bending
neutral line Mc in the same manner as the compression stress,
becomes largest in the outer surface A, and becomes smaller toward
the inner side. Accordingly, it is desirable to make the tensile
strength of the fiber in each of the one-way fiber reinforced resin
layers of the fiber intersection lamination portion 8 larger toward
the outer side, in correspondence to the internal stress state of
the resin member FR1 mentioned above, Therefore, it is possible to
improve the durability while maintaining the product cost in the
same manner as mentioned above.
Specifically speaking, on the assumption that the tensile strength
of the fiber of the one-way fiber reinforced resin layer in the
fiber intersection lamination portion 8 is sequentially set to
.sigma.t1, .sigma.t2, .sigma.tn (in this case, n is an integer
equal to or more than 3) from that arranged in the inner side, it
is desirable to satisfy the following expressions (3) and (4).
.sigma.t1<.sigma.t2<<.sigma.tn (3) .sigma.t1<.sigma.tn
(4)
In particularly preferable, it is desirable that the expression (3)
is expressed by the following expression (3)' and the tensile
strength is differentiated in each of the layers.
.sigma.t1<.sigma.t2<.sigma.tn (3)'
Further, in these cases, it is desirable that a difference
(.sigma.tn-.sigma.t1) between the tensile strength .sigma.tn of the
fiber f in the outermost side one-way fiber reinforced resin layer
L1, and the smallest tensile strength .sigma.t1 in the other
one-way fiber reinforced resin layer is preferably equal to or more
than 0.20 GPa, more preferably equal to or more than 0.25 GPa, and
further preferably equal to or more than 0.30 GPa, and upper limit
thereof is preferably equal to or less than 0.60 GPa, more
preferably equal to or less than 0.55 GPa, and further preferably
equal to or less than 0.50 GPa. If the difference is less than 0.20
GPa, it is impossible to apply a sufficient strength difference,
and it is hard to achieve the cost reduction. On the contrary, if
it is more than 0.60 GPa, the strength difference becomes too
large, and the breakage or the like tends to be generated in the
other one-way fiber reinforced resin layer.
Further, the resin member FR1 in the crown side intends to achieve
a weight saving (a thickness saving) while securing a rigidity
required for the gold club head. Accordingly, on the assumption
that the elastic modulus (the elastic modulus in tension) of the
fiber of the one-way fiber reinforced resin layer in the fiber
intersection lamination portion 8 is sequentially set to E1, E2, .
. . En (in this case, n is an integer, or integral number equal to
or more than 3) from that arranged in the inner side, it is
desirable to satisfy the following expressions (5) and (6).
E1.ltoreq.E2.ltoreq. . . . .ltoreq.En (5) E1<En (6)
In particularly preferable, it is desirable that the expression (5)
is expressed by the following expression (5)', and the elastic
modulus in tension is differentiated in each of the layers.
E1<E2<En (5)'
In this case, if a ratio of the elastic modulus (En/E1) is too
large, the strength in the inner layer is lowered. On the contrary,
if it is too small, the strength in the outer layer tends to be
lowered. Although not being particularly limited, it is desirable
that the ratio (En/E1) of the elastic modulus is preferably equal
to or more than 1.50, more preferably equal to or more than 1.75,
further preferably equal to or more than 2.0, and particularly
preferably equal to or more than 2.25, and it is desirable that an
upper limit thereof is preferably equal to or less than 4.0, and
more preferably equal to or less than 3.0.
In this case, as shown in FIG. 11, in the case of a carbon fiber,
if the elastic modulus in tension is more than 343 GPa, there is a
tendency that the tensile strength is lowered. Accordingly, it is
desirable that the elastic modulus of the fiber f is preferably
smaller than 343 GPa. In the case that the elastic modulus in
tension is smaller than 343 GPa, the tensile strength of the carbon
fiber f is improved approximately in accordance with an increase of
the elastic modulus in tension. Therefore, it is desirable that a
lower limit of the elastic modulus in tension of the fiber f is
preferably equal to or more than 196 GPa, more preferably equal to
or more than 245 GPa, and further preferably equal to or more than
294 GPa.
The compressive strength, the tensile strength and the elastic
modulus in tension of the fiber mentioned above can be
appropriately set by differentiating a fiber material, a filament
diameter, a twisting method, a structure of the toe (bundle) and
the like.
Further, each of the one-way fiber reinforced resin layers L1 to L4
can be formed by a sheet-like one-way prepreg Pa bound by orienting
the fiber f in one direction in an uncured matrix resin R, as shown
in FIGS. 12(B) to 12)(E). The one-way prepreg Pa has an array body
of the fiber f oriented only in one direction. In this example, the
angle .theta. of the fiber f is sequentially set to +45 degrees,
-45 degrees, +45 degrees and -45 degrees from the outer side. Each
of the one-way prepregs Pa is worked in an outline having a
predetermined shape in correspondence to a shape of an opening
portion O in the head main body M, as shown in FIGS. 12(B) to
12(E), and the angle .theta. of orientation of the fiber f with
respect to the base line BL in the head longitudinal direction is
set as mentioned above at that time. Further, the fiber
intersection lamination portion 8 can be formed by applying a heat
and a pressure to the prepreg laminated body in which the one-way
prepreg Pa is overlapped.
In the same manner, the intersection fiber reinforced resin layer
L5 constituting the fiber woven portion 9 can be structured by at
least one cross prepreg Pb as shown in FIG. 12(A). The cross
prepreg Pb includes fibers fa and fb which are oriented in two
directions in one sheet so as to intersect with each other, and
these fibers are previously woven in a woven fabric shape. In the
cross prepreg Pb mentioned above, it is possible to inhibit the
fiber from being disassembled at a forming time when the heat and
the pressure are applied, and a uniform elongation can be easily
obtained. As a result, employing it in the outermost layer of the
resin member FR1 as mentioned above serves for preventing a
defective molding such as a wrinkle and a bending.
The outline shape of each of the prepregs P can be appropriately
set in correspondence to the shapes of the opening portion O and
each of the receiving portions 10b and 11b. In this example, there
is exemplified the structure in which a plurality of slits are
provided for bending a peripheral edge in the side portion side of
each of the prepregs P so as to easily form the trailing portion
13.
Further, the resin member FR1 in the crown side can be formed in
accordance with various methods. For example, as shown in FIGS.
12(A) to 12(E), the laminated body formed by overlapping a
plurality of prepregs P can be formed in a desired shape by
applying predetermined temperature and pressure. The formed resin
member FR1 in the crown side can be firmly fixed to the crown
receiving portion 10b and the side receiving portion lib of the
head main body M, for example, by using an adhesive agent.
Further, the resin member FR1 in the crown side can be formed in
accordance with an internal pressure molding method In accordance
with the internal pressure molding method, a head base body 1A is
prepared first by attaching a laminated body Ps of the prepreg P to
the opening portion O of the head main body M. The head base body
1A is put in a metal mold 20, for example, constituted by an upper
mold 20a and a lower mold 20b which can be separable. The head main
body M is previously provided with a through hole 23 communicating
with the hollow portion i in the side portion 6 or the like, and an
expandable and shrinkable bladder C is inserted therefrom. At this
time, it is desirable to previously apply a thermosetting type
adhesive agent, a primer and the like between the laminated body Ps
of the prepreg and each of the receiving portions 10b and 11b.
Thereafter, as shown in FIG. 14(B), the metal mold 20 is closed and
heated, and the bladder C is expanded and deformed in the hollow
portion i. Accordingly, the laminated body Ps of the prepreg
exposed to the heat and the pressure from the bladder C is formed
as the resin member FR1 in the crown side having a predetermined
shape along a cavity of the upper mold 20a, and is integrally
bonded to each of the receiving portions 10b and 11b. After
molding, the bladder C is deflated, and is taken out from the
through hole 23. Further, the through hole 23 is appropriately
closed by a cover or the like.
Further, in the case of using the internal pressure molding method,
for example, as shown in FIG. 15, it is desirable to previously
attach an auxiliary prepreg 24 to an inner surface 25 directed to
the hollow portion side of the crown receiving portion 10b and/or
the side receiving portion lib (in the example shown in FIG. 15,
the auxiliary prepreg 24 is not illustrated in the side receiving
portion 11b). The auxiliary prepreg 24 is firmly fixed so as to
have a protruding portion 24a protruding from an edge of the
opening portion O to the opening portion O side. Further, it is
desirable that the auxiliary prepreg 24 is separated in a tape
shape as illustrated, or is formed in a ring shape (not shown),
thereby improving an attaching operability to the inner surface of
the head main body.
Accordingly, as shown in FIG. 3, the peripheral edge portion of the
resin member FR can be formed as a fork shape pinching each of the
receiving portions 10b and 11b, in particular, a fork portion 26
having an outer piece portion 26a extending along an outer surface
side of the head main body M and an inner piece portion 26b
extending along an inner surface side thereof. As mentioned above,
it is possible to form the fork portion 26 in the peripheral edge
portion of the resin member FR1 in the crown side in accordance
with a simple procedure, and it is possible to obtain a physical
engaging effect of the head main body M and the resin member FR so
as to improve a bonding strength, by including a step of previously
arranging the auxiliary prepreg sheet 24 having the protruding
portion 24a in the inner surface side of the receiving portion 10b
or 11b at the time of manufacturing the head 1.
It is more effective that the head 1 in accordance with the present
embodiment is applied to a head volume equal to or more than 200
cm.sup.3, more preferably equal to or more than 300 cm.sup.3, and
further preferably equal to or more than 350 cm.sup.3. If the head
volume is less than 200 cm.sup.3, a moment of inertia is reduced,
and a sweet spot area is reduced. On the other hand, if the head
volume is too large, the weight is increased and the height of the
sweet spot SS becomes equal to or more than 38 mm, so that the ball
tends to be hit with backspin and at a low flying angle. It is
desirable that the head volume is preferably equal to or less than
500 cm.sup.3, more preferably equal to or less than 480 cm.sup.3,
and further preferably equal to or less than 470 cm.sup.3.
The description is given above of the embodiment in accordance with
the present invention, however, the present invention is not
limited to the embodiment mentioned above, and can be applied, for
example, to an iron type golf club head and a utility type golf
club head having a hollow structure, and further to a putter type
golf club head. Further, in the embodiment mentioned above, there
is shown the structure in which the resin member constituted by the
fiber reinforced resin is constituted by the resin member FR1 in
the crown side, however, it goes without saying that the resin
member may be arranged, for example, in the side portion and the
sole portion. Further, the thickness of each of the resin member
FR, the head main body M and the like can be appropriately
determined in accordance with general rule.
In order to confirm the effect of the present invention, a wood
type driver head having the head volume of 430 cm.sup.3 is
manufactured by way of trial on the basis of the specification in
Table 1. A shape and the specification of the head main body and
the resin member are shown in FIGS. 1 to 5 and the following
description.
<Head Main Body>
Material: Ti-6Al-4V
Manufacturing method: integral molding in accordance with a lost
wax precise casting method
<Resin Member In Crown Side>
Manufacturing method: internal pressure forming method
Number of used prepreg: five
The fiber intersection lamination portion uses four one-way
prepregs and an angle of orientation of the fiber is shown in
Table.
The fiber woven portion uses one plain woven cross prepreg. The
angle of orientation of the fiber is set to 0 degrees and 90
degrees in the example in Table 1 and set to +45 degrees in the
example in Table 2.
Fiber material: carbon fiber
Elastic modulus in tension of fiber: 240.3 GPa
Thickness of resin member in crown side after being formed: about
0.8 to 0.9 mm
Base resin of matrix resin: epoxy resin
Repulsing performance and durability are tested with respect to
each of the trial heads manufactured on the basis of the
specification mentioned above. The methods therefore are as
follows.
<Repulsing Performance>
The repulsing performance of the head is measured in accordance
with Procedure for Measuring the Velocity Ratio of a Club Head for
Conformance to Rule 4-1e, Revision 2 (Feb. 8, 1999) of U.S.G.A. The
larger the numeric value is, the better the performance is.
<Durability>
A 45 inch wood type club is manufactured by way of trial by
attaching each of the trial heads to a carbon shaft MP-200 (Flex R)
manufactured by SRI Sports Ltd., and is attached to a swing robot
(Short Robo IV) manufactured by MIYAMAE CO., LTD., thereby hitting
the golf ball at a head speed of 51 m/s and a face center position.
The number of the balls until the head is broken is measured.
Results of test are shown in Table 1 and Table 2.
TABLE-US-00001 TABLE 1 Example 3 Comparative Comparative
Comparative Example 1 Example 2 Based on Example 1 Example 2
Example 4 Specification of prepreg FIG. 12 FIG. 12 FIG. 12 FIG. 12
FIG. 12 FIG. 12 Innermost Angle of orientation of fiber .theta.
[deg] 45 45 45 45 45 45 layer Compressive strength .sigma.c1 [GPa]
1.6 1.6 1.6 1.0 1.0 1.6 Tensile strength .sigma.t1 [GPa] 2.0 2.0
2.0 6.0 6.0 2.0 Elastic modulus in tension [GPa] 98 98 98 343 343
98 Second Angle of orientation of fiber .theta. [deg] -45 -45 -45
-45 -45 -45 layer from Compressive strength .sigma.c1 [GPa] 1.3 1.0
1.5 1.1 1.0 1.6 inner side Tensile strength .sigma.t1 [GPa] 3.0 2.0
3.0 4.0 6.0 2.0 Elastic modulus in tension [GPa] 147 98 127 245 343
98 Third Angle of orientation of fiber .theta. [deg] 45 45 45 45 45
45 layer from Compressive strength .sigma.c1 [GPa] 1.1 1.0 1.4 1.3
1.0 1.6 inner side Tensile strength .sigma.t1 [GPa] 4.0 2.0 4.0 3.0
6.0 2.0 Elastic modulus in tension [GPa] 245 98 147 147 343 98
Fourth Angle of orientation of fiber .theta. [deg] -45 -45 -45 -45
-45 -45 layer from Compressive strength .sigma.c1 [GPa] 1.0 1.0 1.3
1.6 1.0 1.6 inner side Tensile strength .sigma.t1 [GPa] 6.0 6.0 4.5
2.0 6.0 2.0 Elastic modulus in tension [GPa] 343 98 196 98 343 98
Fifth Angle of orientation of fiber .theta. [deg] None None 45 None
None None layer from Compressive strength .sigma.c1 [GPa] 1.2 inner
side Tensile strength .sigma.t1 [GPa] 5.0 Elastic modulus in
tension [GPa] 245 Sixth Angle of orientation of fiber .theta. [deg]
None None -45 None None None layer from Compressive strength
.sigma.c1 [GPa] 1.1 inner side Tensile strength .sigma.t1 [GPa] 5.5
Elastic modulus in tension [GPa] 294 Seventh Angle of orientation
of fiber .theta. [deg] None None 45 None None None layer from
Compressive strength .sigma.c1 [GPa] 1.0 inner side Tensile
strength .sigma.t1 [GPa] 6.0 Elastic modulus in tension [GPa] 343
Results Coefficient of restitution 0.839 0.838 0.839 0.839 0.839
0.838 of test Durability 6720 5714 7121 1910 2659 3331 Sweet spot
height [mm] 33.0 33.0 34.8 33.0 33.0 33.0
TABLE-US-00002 TABLE 2 Example 7 Comparative Comparative
Comparative Example 5 Example 6 Based on Example 3 Example 4
Example 8 Specification of prepreg FIG. 13 FIG. 13 FIG. 13 FIG. 13
FIG. 13 FIG. 13 Innermost Angle of orientation of fiber .theta.
[deg] 90 90 90 90 90 90 layer Compressive strength .sigma.c1 [GPa]
1.6 1.6 1.6 1.0 1.0 1.6 Tensile strength .sigma.t1 [GPa] 2.0 2.0
2.0 6.0 6.0 2.0 Elastic modulus in tension [GPa] 98 98 98 343 343
98 Second Angle of orientation of fiber .theta. [deg] 0 0 0 0 0 0
layer from Compressive strength .sigma.c1 [GPa] 1.3 1.0 1.5 1.1 1.0
1.6 inner side Tensile strength .sigma.t1 [GPa] 3.0 2.0 3.0 4.0 6.0
2.0 Elastic modulus in tension [GPa] 147 98 127 245 343 98 Third
Angle of orientation of fiber .theta. [deg] 90 90 90 90 90 90 layer
from Compressive strength .sigma.c1 [GPa] 1.1 1.0 1.4 1.3 1.0 1.6
inner side Tensile strength .sigma.t1 [GPa] 4.0 2.0 4.0 3.0 6.0 2.0
Elastic modulus in tension [GPa] 245 98 147 147 343 98 Fourth Angle
of orientation of fiber .theta. [deg] 0 0 0 0 0 0 layer from
Compressive strength .sigma.c1 [GPa] 1.0 1.0 1.3 1.6 1.0 1.6 inner
side Tensile strength .sigma.t1 [GPa] 6.0 6.0 4.5 2.0 6.0 2.0
Elastic modulus in tension [GPa] 343 98 196 98 343 98 Fifth Angle
of orientation of fiber .theta. [deg] None None 90 None None None
layer from Compressive strength .sigma.c1 [GPa] 1.2 inner side
Tensile strength .sigma.t1 [GPa] 5.0 Elastic modulus in tension
[GPa] 245 Sixth Angle of orientation of fiber .theta. [deg] None
None 0 None None None layer from Compressive strength .sigma.c1
[GPa] 1.1 inner side Tensile strength .sigma.t1 [GPa] 5.5 Elastic
modulus in tension [GPa] 294 Seventh Angle of orientation of fiber
.theta. [deg] None None 90 None None None layer from Compressive
strength .sigma.c1 [GPa] 1.0 inner side Tensile strength .sigma.t1
[GPa] 6.0 Elastic modulus in tension [GPa] 343 Results of
Coefficient of restitution 0.841 0.840 0.841 0.840 0.841 0.839 test
Durability 6500 5850 7215 1820 2704 3127 Sweet spot height [mm]
33.0 33.0 34.8 33.0 33.0 33.0
As a result of the tests, it is possible to confirm that the golf
club head in accordance with the embodiment improves the durability
without changing the sweet spot height or the like. Further, there
is no significant reduction of the repulsing performance.
* * * * *